In programming, what is the main characteristic of a global variable?

A global variable is characterized primarily by its scope, which allows it to be accessed from anywhere within the program, making it retain its value throughout the program's entire execution. This means that once a global variable has been declared and assigned a value, that value remains accessible and can be modified by any part of the program that references it. This persistent nature of global variables is essential in many programming scenarios, where maintaining state or sharing data between different functions or modules is necessary.

Using a global variable effectively allows for flexibility in programming, as it provides a way to store values that need to be persistent and widely reachable throughout the codebase. The retention of its value until the program concludes differentiates it significantly from local variables, which are limited in scope to the block of code in which they are declared and are discarded once that block is exited.